Make unreachable() only panic in safe mode.

lib/std/core/builtin.c3

@@ -204,8 +204,9 @@ macro void unreachable(String string = "Unreachable statement reached.", ...) @b
 {
 	$if env::COMPILER_SAFE_MODE:
 	panicf(string, $$FILE, $$FUNC, $$LINE, $vasplat);
-	$endif;
+	$else
 	$$unreachable();
+	$endif
 }
 
 <*

releasenotes.md

@@ -33,6 +33,7 @@
 - Fixes to `@format` checking #2199.
 - Distinct versions of builtin types ignore @operator overloads #2204.
 - @operator macro using untyped parameter causes compiler segfault #2200.
+- Make `unreachable()` only panic in safe mode.
 
 ### Stdlib changes
 - Deprecate `String.is_zstr` and `String.quick_zstr` #2188.